Techniques related to rendering annotations of large images are discussed below. Very large images can contain billions of pixels. These large images, sometimes called gigapixel images, may be difficult to navigate and view with conventional technology. Specialized software has recently been developed to facilitate smooth and rapid panning and zooming of large images. With such software, typically only a small fraction of an image is viewable at one time. For example, when viewing a 5 gigapixel image on a 1 megapixel screen, only 1/5000th of the pixel data is viewed at one time.
To improve the experience of navigating a large image, annotations may be added and displayed as the image is navigated. Annotations are various forms of media such as text, sound, etc., that may be associated with some object in an image. Problems related to rendering annotations while navigating large images have not been addressed. For example, because there can be significant changes in scale when zooming in and out of a large image, simplistic rendering schemes can result in overly large or small text, sound played when the object associated with the sound is not in view. Other problems may occur. Described below are techniques related to creating and rendering annotations in a system for navigating images.